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Chapter 53

Chapter 53 Communities. Chapter 53. Community Ecology. I. Community. A group of populations of various species living close enough for potential interactions to take place. competition predation herbivory symbiosis disease. Gause’s competition theory.

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Chapter 53

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  1. Chapter 53 Communities Chapter 53 Community Ecology

  2. I. Community A group of populations of various species living close enough for potential interactions to take place. • competition • predation • herbivory • symbiosis • disease

  3. Gause’s competition theory • The “Competitive Exclusion Principle” was derived based on the research of Parameciumcaudatum and aurelia. • Having a slight reproductive advantage can lead to elimination of a species. • Resource partitioning can lead to niche differentiation.

  4. Joseph Connell and species niche/competition

  5. Predation • The adaptations of both predators and prey tend to be refined through natural selection. • Cryptic and aposematic colorations act as defensive adaptations. • Batesian and Mullerian mimicry are used by both prey and predators.

  6. II. Community Structure The structure and dynamics of a community depend largely on feeding relationships. ie. Food webs/chains ** The energetic and dynamic stability hypotheses propose limits to any feeding relationship.

  7. Other factors that affect community structure and dynamics are • dominant species • keystone species • foundation species

  8. In an attempt to understand relationships between adjacent trophic levels, knowledge about community organization is useful. • Bottom-up and Top-up models define community organization. • Many intermediate models are possible.

  9. III. Disturbances • An event, storm, fire, flood, etc., can cause changes in a community. • Although most seem negative, some disturbances create opportunities for increased species diversity (intermediate disturbance hypothesis) • Ecological succession is the result of changes in the community structure.

  10. IV. Community structure models 1.Intergrated hypothesis: communities exist as closely linked group, locked into association by biotic interactions, therefore functioning as a unit.

  11. 2. Individualist hypothesis: community structure based on a chance grouping of organisms that rely on the same abiotic resources. • rivet model: organisms are so dependent on each other that the reduction or increase of one affects the others. • redundancy model: species are redundant, “if one predator disappears, another one will take its place”.

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